From what I can remember the novel is like solo leveling in the sense it is a world where people have abilities and magic and monsters are invading the world. The main character is one of the strongest but finds being the strongest makes you the loneliest.
His ability or job was magic swordsman and he is only just able to defeat a demon lord but it's still not enough.
At the start of the story him and a former friend are sent back in time to before the monsters came both with their memories of the future intact but he does not want the former friend knowing. This means he is a normal person again.
Major plot points I can remember are: The former friend gets the magic swordsman class and the MC gets a stronger one.
The MC can transport himself into the body of the demon lord who he fought in the future and there are more demon lords fighting for supremacy and the one he finds himself in had been asleep for 100 years.
At one point the MC as demon lord buys a dragon egg from a auction that is supposed be faulty but has twins instead off just one. One is magic orientated and the other has high stats in strength which is sent to the human world so he can take care of it.
The MC obtains a bracelet named Jörmungandr in the shape of a snake from a treasury.